It's interesting to see the performance results you got - for most substantial applications , Rules Engines should run faster the equivalent Java Code. This is not only due to the Rete optimisation , but also the business logic doesn't get scattered / repeated / run more times than necessary (esp in applications with many changes to their logic over time).
Don't let the XML Format fool you - the examples could equally have been written in Java (manipulating the Drools API) or Excel. The important thing is that you state what you know to be true rather than exactly how you do it. I'm a Java/J2EE programmer as well , and I'm suggestng Drools as a way to make things easier , not just introduce another (XML) file format.